In general, the Theorema brand tends to be characterized by highly intricate watch face designs that show off a series of gears and dials, with the casing itself being silver or gold.
The dials in particular are especially gorgeous, featuring deep blue sapphire and, in cases like the Sao Paulo, artistic renderings of the sun and moon, among other things.
These models tend to have metallic bands and are designed with more formal and business settings in mind.
The Pionier models, by contrast, tend to be a bit more casual and made with the idea of everyday and even sportswear in mind.
Instead of the metallic bands and bigger design of the Theorema models, these pair leather bands with slimmer cases.
This makes it easier to pair these watches with something other than formal wear.
Both the Theorema and Pionier tend to be waterproof, though the exact depths to which they are cleared for use is actually harder to determine.
The same holds true with the exact type of mechanism powering its movement.
That said, some models blend the line between these distinctions.
For example, the Theorema Casablanca pairs a large, gear-showing watch face with a leather strap.